Method of making composite wire



May 23, 1950 E. H. WALLACE METHOD OF' MAKING COMPOSITE WIRE Filed July 24, 1946 am @waak Patented May 23, 1950 METHOD OF MAKING COMPOSITE WIRE Edward H. Wallace, Detroit, Mich., assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey f Application July 24, 1946, Serial N0. 686,044

1 Claim.

This invention relates to a composite wire, and in particular it relates to an aluminum conductor wire having a tin outer surface and to a process for producing the same.

Aluminum wire, because of its high electrical conductivity and because of its lightness, is particularly useful as a medium for conveying electrical energy. However, aluminum wire as such possesses the objectionable feature of being diicult to solder, such as in the formation of good v electrical joints. Certain special uxes and compounds have been used to facilitate soldering aluminum, but the materials and methods commonly available for joining copper wire will not function with aluminum. As a result of this deflciency the advantages oi the use of aluminum wire has not materialized. In accordance with the practice of my inven tion, I provide an aluminum wire and a process for treating such wire so that the wire may be readily soldered by employing conventional soldering methods. In general, my invention includes the steps of treating aluminum Wire in such a manner as to permit the adhesion of electrodeposited iron thereon. After the iron is deposited, the coated aluminum wire is treated by tinning the surface of the electrodeposited iron. This tinning operation may be performed by electrodeposition or by dipping the wire directly into a hot tinning bath. The coatings of iron and tin are relatively thin and do not interfere substantially with the predominating characteristics of the aluminum wire. It is therefore possible by my process to produce an aluminum wire useful for electrical purposes, and which not only may be used competitively with conventional copper wire but provides the highly desirable feature of light weight.

The reason for providing the aluminum wire with a thin lm of iron electrodeposited upon the aluminum is that tin will not bond satisfactorily to an aluminum surface.

Among the objects of my invention are to provide an aluminum wire having soldering characteristics comparable to that of the conventional tinned copper wiring; to provide an easily solderable wire having high electrical conductivity and which is light in weight; to provide a tinned aluminum wire in which a high degree of adhesion is obtained between the tin and4 the aluminum by the use of an intermediary film; to provide a composite aluminum wire having a tinned outer surface and underlying intermediary surface in which the tinned layer and intermediate layer form no substantial change in the thickness or to. .should be slightly greater because it is necessary These and other objects and advantages will appear more fully in the following detailed description when considered in connection with the accompanying drawing, in which:

Figure 1 illustrates an aluminum wire forming an embodiment of vmy invention; and

Figure 2 is a diagrammatic view illustrating a process useful in the formation of the coated aluminum wire.

With reference to the drawing and in particular to Figure 1, I illustrate an embodiment oi' my invention in the form of solderable aluminum wire in which the number I designates an aluminum wire or core. By reference to aluminum, I contemplate pure aluminum and aluminum alloys in which aluminum is the predominating metal. As shown in Figure 1, the surface 2 of the aluminum is treated so as to permit the adhesion of electrodeposited iron 3 thereon. After a flash plate of the iron 3 is deposited on the treated aluminum, the wire is immersed into a bath capable of forming an electrodeposit of tin 4 on the iron surface. It is to be understood,

however, that instead of electrodepositing the tin on the iron surface, the tin may be applied directly to the iron in a dipping operation of the wire in hot tin. Also, the tin may be applied by first producing a flash electrodeposit of tin on the iron surface and thereafter building up the thickness of the tin deposit by means of dipping the coated wire in a hot tin bath.

In coating the aluminum wire with a layer of electrodeposited iron, it is merely necessary that -the deposited iron have a thickness of approximately .0003 inch to enable the tin to bond there- The thickness of the tin deposited., however,

for the tin coating to be subjected to ordinary wear and handling, particularly at those locations where the wire is to be soldered. The thickness of the tin,'therefore, should be in the order of .001 inch. Since, according to my invention, the deposited layers of metal or other treatments are performed in a continuous operation, it is also possible in the same continuous operation to coat the wire with a suitable electrical insulating covering 5. The covering may be in the form of extruded rubber or synthetic rubber, or

the wire. This degreasing operation is conductedl`v` by the vapor method in which tri-ethylene chloaman? Oz. per gal. Stannous sulphate i 13 Sulphuric'acid 4 Tartaric acid' 4 5,A Glue .4 to .8 Cresol .8

ride is heated within a container (i1and:the'vap'orsfy therefrom react upon the wire for degreasing, purposes.

Following the degreasing operation the aluminum-'Wire is carried over a series' 2 of rollers Tinto successivel stages of? operation 'for 'treatingY` the aluminum prior tf1-:plating: Aftersthe aluminum Wire is cleaned' the avire^entersarit'anltfccntain; ing-a bath or .r solution: raised-'izto'thefboiling' point. An exampleoi such a1 solution. contained in the tank 8' comprises 2.5 :gramsz'per: liter ofchromic oxide andu99V cc; .pen liter'o sulphuri'c acid. This treatment is primarily a cleaning operation" for removing any? oxide deposits Apreviously formed on thel surface of." thewire, and iforproviding a uniform basev onto* which ther next. coatingl is formed; Followingthisfoperatiorr the-aluminum wireiszrinsed inrclean^-hot Water.l This takes piacerinacontainerr;

The' nextfstep :in the-f treatment: of f the aluminumdsto produce thereonoxide coated surface: This issaccomplishedby` treatingthe Wire in "a container' lrofffan alkali'solutioncomprising an alkalimetal carbonate andY a chromate. Anexample ofthe composition-used vin this so'- lution is'sodium carbonate and potassium dichromatefin a .ratio-of 3-to .1.

Thefwire is. rinsed4 by |conducting the wire through a bath Il .of water.

of theoxide coatingaonrthe aluminum wire. In this operation thewire is dipped intoA a bath I2 containing about5% to 70% nitric acid to etch the oxide. coating so that an electro-plated coating will bond'rmly thereto; Following this operation the aluminum wire` is againrinsed in clean water I3 and it is `ready'forthe electroplating operation. Ihave found that in order to obtain a good'bond 'between aluminum and other metals, it is ldesirable to'rst coat'the treated aluminum with a layer of electrodeposited iron. This is accomplished in the bath I4. The elec- 'troplatingof-'the iron fto thealuminum may be carried Aon' ini any recognized iron' plating solution; Goodresults-can be' obtainedf'byusing a solution consisting'essentially-of Y3255120 425 Ygrams perliter offerrouschloride-and 125 grams per liter=of calcium chloride. An ironfflash Vdeposit as thin as .0091 inch 4will produce satisfactory results. for subsequently forming a-.bond with the electrodeposited Preferably, however, the electrodeposited iron should have .athickness in the ordervofrLOOOS-.OOOS inch.. Vllollovving the flash 'iron plate, the Wire is again rinsedina. water lows, wherein per gal. means' per gallon of water:

A--nalstep'irr-the treatment of the compositionwire is--todip=the wire into a bath of hot wateresolas to remove all traces of the solution fofythe'vbath.. Thereafter the Wire is completed and if desired, it may be coated with insulating material'fin accordance with conventional practices.. As a modiiied form of the invention, the Wire, after it leaves the hot water bath Il, may be immersed into a hot tin bath (not shown). s0 that .the tin may be built .up to..`the.d esired'thiclc ness at a more rapid rate than: that possiblein the electrodeposition of the tin.

It,is to beunderstood that the wire. as thus produced, in accordance with the practice of my invention, possesses Va,V highY degree of'bond betweenV the adjacentl layers sothatthe Wire in effect is an' integral unit capable Oibeing bent andY manipulatedin substantially' the lsame mannerl as untreatedV aluminum` Wireand" with the added feature ofthe' wire-*being-'liglit in weight and "readily solderable.

As thus shown and described' itfis believed apparent that I"have provided a novel arrange'- ment wherebyaluminum Wire-'is converted so as tty-'possess all f of the' desirable characteristicsv of tinned copper Wire plusthef exceptional advantageousr characteristic of *lightness Wiile I have shown and" described a preferred embodiment and "process of'my invention, itfis-t to Rb'e* understood that it is' susceptible of those vmodiiications` Whichappear obviously Within the spirit of the' invention and as appearing' in' the scope of the appendedf claim'.

' Hvin 'th sid ib'edl` .finvention' h t"I Thenextstep in the .operationislthetreatment o a g u escr my W a' claim and desiretoprotect rby lietters Patent is.

lThe methodl of'- forming a' tinn'edo-aluminum conductorv wire ofV composite.`- laminae'I in' which adjacent layers" of deposited '.'meta'ls' are' securely bonded togetheru comprisingr'theff steps; cleaning the` aluminumfwiref with" asolutioni containing` a small amount of" chromi'c'" oxide Vand sulphuric acid; then immersing thexwlrefin' a'y solution of an alkali' metal carbonate and? ak chromate; to provide an oxide .coati on thef aluminum, then treating the f Wire` vwithT nitric' acidi tor etch the oxide coat;` then eleot'rodepositin'gi a'ilayer 'of Airon on the etched surface, and finally applying over the irornaprotecting coating EDWARD WAILACE;

REFERENC-ES-:- CITED The*r following'refererrces arefof recordin the iii-e ofi this patents" UNITED STATES' PATENTS Number Namey Date 440,952 Land,. .Nov. ,18; 189D 628;? CowperfGolesr. July,1.1, 1899 .1,925,318 Work @,ct..9=, 1934 1,988,645 Bowden; ,Jan..22, 1935 2,055,393 Thomas .Sept.;22,..1936 2,162,789 Rauh.. Jeune .2.0, 1939 2,233,410 Frasch Mar. 4 1941 FOREIGN- PATENTS' Number Country; Date 3,439' Great Britain .of 1910 5485330v GreatBritain' of 19242 

